New chiral phosphinite ligands with C₂‐symmetric axis and their possible applications in Ru‐catalyzed asymmetric transfer hydrogenation

Abstract

Abstract The new chiral ligands N , N ′‐bis‐[(1 R )‐1‐ethyl‐2‐ O ‐(diphenylphosphinite)ethyl]ethanediamide, 1, and N , N ′‐bis‐[(1 S )‐1‐isobutyl‐2‐ O ‐(diphenylphosphinite)ethyl]ethanediamide, 2, and the corresponding ruthenium complexes 3 and 4 were prepared and their structures were elucidated by a combination of multinuclear NMR spectroscopy, IR spectroscopy and elemental analysis. Following activation by NaOH, these chiral ruthenium complexes serve as catalyst precursors for the asymmetric transfer hydrogenation of acetophenone derivatives in i PrOH. The complexes 3 and 4 showed high catalytic activity but low selectivity in asymmetric transfer hydrogenation reactions. Copyright © 2009 John Wiley & Sons, Ltd.